Tunable surface chemistry and wettability of LDPE substrate

Octafluorocyclobutane and acrylic acid (C4F8-co-AA) have been plasma copolymerised onto low-density polyethylene (LDPE) and glass slides under various pulsation periods of radio frequency pulsed plasma. The surface wettability of plasma polymer coating is traditionally considered as a substrate-independent property.

The high concentration of the carboxylic acid functional groups gave rise to hydrophilicity via lowering duty cycle, and substrate impact gave rise to hydrophobicity for ultrathin coatings.

Wetting stability for ultrathin coatings
The X-ray photoelectron spectroscopy and coating thickness measurements confirmed that the sudden increase in water contact angle for the lower duty cycle is influenced by the hydrophobic substrate for ultrathin polymer coatings. It was highlighted that the precise control over the surface wettability is attained by tuning the plasma parameters. The substrate-dependent wettability for flat substrate persisted for longer than 8 weeks, which demonstrates wetting stability for ultrathin coatings.